In a utility vehicle, when an engine load is engine rated torque or less, the torque is matched with an engine output torque in a high-speed control field in a torque diagram. For example, target engine speed is set in correspondence with setting of a fuel dial, and a high-speed control field corresponding to the set target engine speed is determined.
Alternatively, a high-speed control field is determined in correspondence with the setting in the fuel dial, and the target engine speed of the engine is set in accordance with the determined high-speed control field. Then, control for matching the engine load and the engine output torque is performed in the determined high-speed control field.
Generally, to increase the operation amount, many operators set the target engine speed such that it becomes equal to the rated engine speed of the engine or engine speed close to the rated engine speed in many cases. A field where the amount of fuel consumed of the engine, i.e., a field where fuel economy is excellent normally exists in a medium speed engine speed field or a high torque field on a torque diagram of the engine. Therefore, a high-speed control field which is determined between no-load high idling rotation to rated rotation is not an efficient field in terms of fuel economy.
Conventionally, to drive an engine in a fuel economy field, there is a known control device in which a value of the target engine speed and engine target output torque are previously set in association with each other in each operation mode, and a plurality of operation modes can be selected (see patent document 1 for example). According to the control device of this kind, when an operator selects a second operation mode, the engine speed can be set lower than that of a first operation mode, and fuel economy can be enhanced.
When the operation mode switching system as described above is used, however, the fuel economy cannot be enhanced if an operator operates the mode switching means one by one. If the engine speed of engine when the second operation mode is selected is set as a value of engine speed which is uniformly lowered from the engine speed of the engine when the first operation mode is selected, the following problem occurs if the second operation mode is selected. That is, the maximum speed of an operating device (operating machine, hereinafter) of a utility vehicle is lowered as compared with a case where the first operation mode is selected. As a result, the operation amount when the second operation mode is selected becomes smaller than that when the first operation mode is selected.
Patent Document 1: Japanese Patent Application Laid-Open No. 10-273919